Both active and passive electronic components generate heat when used in electronic circuits. Especially switching converter devices generate heat due to high currents and voltages. For example in a voltage source inverter the output voltage is formed by connecting either negative or positive voltage of a DC-voltage link to the output of the device using multiple of semiconductor switches. The semiconductor switches are operated with a high frequency for producing desired output voltage. Although the semiconductor switches are controlled from fully blocking state to fully conducting state (and vice versa) losses are incurring in the switches during the switching instants. Losses are also generated while the semiconductor switches are conducting.
The DC voltage in the DC-voltage link is sustained using one or more capacitors connected across the negative and positive voltages. When the switches are operated and the output current is changed due to changed state of semi-conductors switches, a current is drawn from the capacitors of the DC-link. Thus the capacitors are constantly discharged and charged when the device is in operation and such capacitor ripple current causes the capacitors to heat.
Other types of passive components that heat up during the use of a voltage source inverter are inductive components. Inductive components are employed as filters to reduce the current ripple and to block high-frequency disturbances from entering to supplying network. The inductive components generate heat as losses are incurring in the magnetic core material when the magnetic flux changes. As current flows through the coil of the inductive components, resistive losses are also produced.
The generated losses heat up the components themselves and also neighbouring and surrounding components. It is known that elevated temperature of the components affects directly to the lifetime of the components. In the worst case, excessive temperature may also directly cause malfunction or destruction of the components.
The heat generated by the components is typically removed from the components by providing different cooling elements which absorb and spread the heat and further dissipate the heat in controlled manner. For example heat sinks may be attached to heat generating components such that the heat from components is led to the heat sink and further removed from the heat sink outside the enclosure of the device in controlled manner. In heat sinks with liquid circulation the heat from the components is led to a circulating liquid and the heat from the liquid is removed at a desired location.
A problem relating to liquid cooling of electronic devices or components is that the heat sinks with conduits for liquids are large in size and require a piping arrangement for leading the cooling liquid to the conduits of the heat sink. Especially if an electronic device comprises multiple of components that require cooling, the arrangement for liquid cooling takes a considerable amount of space inside the housing of the device as multiple of liquid cooled heat sinks are employed.